Staining is a technique frequently used in biology and medicine to highlight structures in biological tissues for viewing, often with the aid of different microscopes. Stains may be used to define and examine bulk tissues (highlighting, for example, muscle fibers or connective tissue), cell populations (classifying different blood cells, for instance), or organelles within individual cells.
Cell staining is used to better visualize cells and cell components under a microscope. By using different stains, one can preferentially stain certain cell components, such as a nucleus or a cell wall, or the entire cell. The stains can be used on fixed, or non-living cells, as well as on living cells.
Cell staining techniques are also often used to detect a pathogen in a blood sample. One important pathogen is the malaria.
The first dye synthesized for detection by staining methylene blue, in 1876. Six years later, it was used to discover tubercle bacillus. Within the years, modifications of MB were employed, including, “ripened” MB in combination with other dyes, such as eosin, which allowed differentiation between blood cells and the nuclei of malarial parasites, as well as the combination of MB methylene blue demethylation with glycerol as a stabilizing agent in methanol solvent, known as the Malachowski-Wright-Giemsa stain.
J. Keiser et al. describe Acridine Orange in comparison to Giemsa stain, for malaria diagnosis, including its diagnostic performance, its promotion and implementation and the implications for malaria control.
U.S. Pat. No. 5,470,751 describes another reagent for staining malaria infected cells and a method for detecting malaria infected cells using the same, wherein the reagent is a staining solution comprising at least one first dye of an Auramine analogue, such as Auramine O and at least one second dye of a condensed benzene derivative, such as 3,3′-diethyl-2,2′-oxacarbocyanine iodide. A test sample is treated with reagent to stain malaria infected cells. The stained malaria infected cells are then optically detected.
In addition, the Centers for Disease Control and Prevention CDC, Diagnostic Procedures, 2009 describes under the heading “Blood specimens: Microscopic Examination” the Kawamoto technique for the detection of blood parasites, such as malaria parasites, using fluorescent dyes that stain nucleic acids. As discussed in this publication, in the Kawamoto technique, blood smears on a slide are stained with acridine orange (AO) and examined with either a fluorescence microscope or a light microscope adapted with an interference filter system. This results in a differential staining of nuclear DNA in green and of cytoplasmic RNA in red, which allows recognition of the parasites.